Buttonhole sewing machine



FIG. 1 is a left side elevational view of a buttonhole sewing machine, showing my new design;

FIG. 2 is a right side elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a front elevational view thereof; and

FIG. 7 is a right front perspective view thereof. 

The ornamental design for a buttonhole sewing machine, as shown. 